The names are in, but in Iran just registering your candidacy is not enough to actually participate in a presidential election.

Now it's time for the biggest hurdle, as the Guardians Council -- the 12-member body at the heart of the Islamic republic -- vets all applications and comes up with a final list of candidates. In the course of days, nearly all of the hundreds of registrants will be rejected, leaving voters around half a dozen handpicked names to choose from on election day (May 19).

As the sifting gets under way, labels will be flying as domestic and foreign media alike try to categorize potential candidates into one of Iran's various political streams. Ultimately, most will be deemed to be incompatible with the state's Islamic values, meaning those who are closest to the Western idea of reform have little chance of advancing.

But while the names that make the final list can be assumed to be acceptable to the clerical establishment, that does not mean there are not bona fide differences among them. But what, exactly, is a reformist, a conservative, or a hard-liner?

There are overlaps between camps, of course: some conservatives, for example, hold more liberal views on, say, the economy. But in lieu of actual parties (there are none in Iran) or self-identifying factions, a handful of terms do serve to delineate the strands of loose political ideology around which Iranian politicians cluster.

Former Iranian President Mohammad Khatami was a prominent Moderate

Reformists: International media often portray this group as Iran's great hope of freeing itself from the tyranny of the supreme leader and his acolytes. But the term is, in itself, inadequate. First, being a "reformer" in the Iranian context means something entirely different than what would be considered a progressive in the West -- we are not talking about people advocating for gay marriage here. There are also two distinct types of reformists in Iran.

Seditionists: The first distinct branch within the reformist camp is comprised of opposition supporters who are seen as the "seditionists" by their foes. For the most part, the seditionists are the leaders and backers of the Green Movement who took to the streets en masse to protest Mahmud Ahmadinejad contentious reelection to a second term in 2009. The conservative media labeled the uprising the fitna (meaning "sedition").

These people -- notably Mir Hossein Musavi, the second-placed finisher who lost a tight race due to what his supporters claimed was electoral fraud -- have long since been ostracized from Iranian politics. This group believes in the predominance of elected institutions over unelected -- a contentious idea in a system in which the clerical establishment plays a dominant role in steering the country -- and argues for the direct election of the supreme leader, the highest authority in the Islamic republic. It is perhaps the hardest camp to define, considering that another stream, the conservative hard-liners, label anyone with even the slightest reformist bent a "seditionist." In their purest form they will play little part in the election, although there are questions whether their most ardent followers could affect the outcome by refusing to vote or by other means.

Moderates: The second "reformist" group is the moderates, which remain firmly within the clerical establishment but also believe that a liberal society with increased participation of the people are in keeping with the Islamic Revolution.

This camp's great hope was once Mohammed Khatami, who served as Iran's president from 1997-2005. Khatami exhibited his desire for reform by extending an olive branch to the United States in 1998 with his then-unheard-of call for a "dialogue of civilizations," and at home by allowing many newspapers to open up.

But key to the moderates, while allowing for some liberalization and greater public participation, is ensuring the continued success of the Vilayat-e Faqih -- the so-called Rule of the Jurists. This political philosophy, developed by the Islamic republic’s founder, Ayatollah Ruhollah Khomeini, holds that those best fit to govern are those most equipped to interpret God’s law -- namely, Iran’s clerics. During the last election, Mohammed Reza Aref, Khatami’s vice president from 2001-2005, represented this group until he withdrew to allow Rohani a better chance of winning. This year, Mostafa Kavakebian, Tehran’s representative in the Majlis (Iranian parliament), best embodies this faction.

Iran's Supreme Leader Ayatollah Ali Khamenei

The Principlists/Hardliners: Known in Iran as the Osul-Garayan, this group congregates around the supreme leader -- currently Ayatollah Ali Khamenei. This group is guided by an unswerving belief in the ideological principles of the 1979 Islamic Revolution. They have a loose manifesto based on loyalty to the fundamental pillars of the Islamic Republic of Iran: Shi'a Islam, the 1979 Islamic Revolution, loyalty to the Supreme Leader, and an unquestioning acceptance of the Vilayat-e Faqih. They are above all suspicious of "cultural invasion" -- what they term Westoxification -- Western social influence that must be resisted at all costs. They fear the West's soft power -- and its possible influence on the population -- at least as much as its hard power, if not more. They believe that Iranians should be ascetic -- material development is treated with suspicion and must be subordinated to the importance placed on spiritual development. This year their most prominent candidate is Ebrahim Raisi, custodian and chairman of the Astan Quds Razavi, the organization that manages several of Iran’s holiest sites.

Pragmatic Conservatives: This group is again comprised of people firmly within the Islamic Republic's clerical establishment. Pragmatic conservatives believe that the Vilayat-e Faqih is the institutional pivot upon which the entire political system should turn, but also that economic reforms are necessary. People should be allowed to get rich; the economy should open up to the world. Perhaps the best exemplar of this camp is Ali Larijani, the current chairman of the Majlis and former secretary of the Supreme National Security Council. Larijani believes utterly in the Islamic Revolution, but also that it must be tempered with economic pragmatism. This year their most prominent potential candidate is Mohammad Bagher Ghalibaf, the mayor of Tehran.

Pragmatists: This group forms a bridge between the hardliners and those more moderately-inclined. Again, they are deeply embedded within the established elites but believe that Iran must open up more to the West, both economically and diplomatically (though they also fear its cultural influence). The undoubted head of this faction is President Hassan Rohani (often described as a relative moderate following the demise of the moderates-turned-seditionists), who faces strong opposition from hard-line elements within the state as he seeks reelection this year. His cause will not be helped by the death earlier this year of Akbar Hashemi Rafsanjani -- one of the most prominent figures in the history of the Islamic Republic and a quasi-mentor of Rohani, who also benefitted from Rafsanjani’s political networks.

Former President Mahmud Ahmadinejad

The Wildcard: On 11 April, former President Mahmud Ahmadinejad surprisingly registered as a candidate, despite Khamenei's express wishes that he do no such thing. Ahmadinejad was once close to the supreme leader and was considered a hard-line principlist. But he was and remains a populist, drawing the majority of his support from Iran's lower classes. It may well be that the Guardians Council keeps him off the final list of candidates, but it would do so at the risk of alienating many voters. And if he does manage to get through (or if the attention he attracts helps boost the chances of his former vice president, Hamid Baghaei) Iran's carefully managed elections may yet throw up one more surprise.

David Patrikarakos is a contributing editor at The Daily Beast and the author of Nuclear Iran: The Birth Of An Atomic State. His work has appeared in The New York Times, The Wall Street Journal, the Financial Times, The Guardian, Politico, Foreign Policy, The Spectator, The New Republic, The New Statesman, and many others.